Light emitting element mounting member, and semiconductor device using the same

ABSTRACT

The object of the present invention is to provide a light-emitting element mounting member and a semiconductor device using the same that is easy to process and that allows adequate heat dissipation.  
     A light-emitting element mounting member  200  includes: a substrate  2  including an element mounting surface  2   a  mounting a semiconductor light-emitting element  1  and first and second conductive regions  21, 22  disposed on the element mounting surface  2   a  and connected to the semiconductor light-emitting element  1;  a reflective member  6  including a reflective surface  6   a  defining an internal space  6   b  for housing the semiconductor light-emitting element  1  and containing a metal disposed on the element mounting surface  1   a;  and a metal layer  13  disposed on the reflective surface  6   a.  The reflective surface  6   a  is sloped relative to the element mounting surface  2   a  so that a diameter of the internal space  6   b  is greater away from the element mounting surface  2   a.

TECHNICAL FIELD

The present invention relates to a light-emitting element mountingmember and a semiconductor device using the same. More specifically, thepresent invention relates to a light-emitting mounting element formounting a light-emitting diode, a semiconductor laser, or the like anda semiconductor device using the same.

BACKGROUND ART

An example of a conventional member for mounting semiconductorlight-emitting elements is described in Japanese Laid-Open PatentPublication Number 2002-232017.

In the semiconductor mounting member described in this publication, asubstrate and a ceramic window frame surrounding a light-emittingelement is formed from a ceramic having as its main component aluminumoxide, aluminum nitride, or the like.

With the increase in output in light-emitting elements in recent years,there has also been an increase in heat generated by semiconductorlight-emitting elements. When a ceramic having aluminum oxide as itsmain component (hereinafter referred to also as alumina) is used in thesubstrate and the window frame, adequate heat dissipation is notpossible, leading to increased temperature.

Furthermore, if aluminum nitride, which has high thermal conductivity,is used, the raw material is more expensive and harder to process thanalumina. Furthermore, if a metallized layer is formed on the surface, ametallized layer having W or Mo must generally be formed first. In suchcases, a method is used in which a metal paste having W or Mo as itsmain component is first applied to a green sheet and then this is firedtogether with the main aluminum nitride ceramic unit (co-firedmetallizing). With this method, however, thermal deformation and thelike take place during firing, making it difficult to precisely form ametallized layer with a fine pattern, e.g., of less than 100 microns.

DISCLOSURE OF INVENTION

The object of the present invention is to overcome the problemsdescribed above and to provide a light-emitting element mounting memberand semiconductor device that uses the same that has high thermalconductivity and that is easy to process.

The present inventors performed various investigations regardinglight-emitting element mounting members that adequately dissipate heatgenerated by semiconductor light-emitting elements and that are easy toprocess. As a result, it was found that preferable characteristics canbe obtained by using a mounting member with high thermal conductivity byincluding metal in a reflective member.

In order to achieve the object described above, a light-emitting elementmounting member according to the present invention includes: a substrateincluding an element mounting surface mounting a semiconductorlight-emitting element and first and second conductive regions disposedon the element mounting surface and connected to the semiconductorlight-emitting element; a reflective member including a reflectivesurface defining an internal space for housing the semiconductorlight-emitting element and containing a metal disposed on the elementmounting surface; and a metal layer disposed on the reflective surface.The reflective surface is sloped relative to the element mountingsurface so that a diameter of the internal space is greater away fromthe element mounting surface.

In a light-emitting element mounting member formed in this manner, thesubstrate serves as a high thermal conductivity member, thus allowingadequate dissipation of the heat generated by the semiconductorlight-emitting element. Furthermore, since the reflective membercontains metal, processing is made easier compared to a structure inwhich the reflective member is formed from ceramic. This makes itpossible to provide a light-emitting element mounting member that iseasier to process.

Also, since the reflective member contains metal, the bond with themetal layer disposed on the reflective surface of the reflective memberimproves. As a result, a light-emitting element mounting member that iseasy to produce can be provided.

It would be preferable for the light-emitting element mounting member tofurther include a bonding layer bonding the element mounting surface andthe reflective member. A heat resistance temperature of the bondinglayer is at least 300 deg C. The bonding layer melts at a temperature ofno more than 700 deg C. and bonds the element mounting surface and thereflective member. In this case, since the bonding layer has a heatresistance temperature of at least 300 deg C., the bonding layer canprevent peeling of the substrate and the reflective member and ispractical even if the temperature when the semiconductor light-emittingelement is mounted on the light-emitting element mounting member is250-300 deg C. Thus, a highly reliable light-emitting element mountingmember can be obtained. Furthermore, since the bonding temperature is nomore than 700 deg C., if metallized patterns formed from Au, Ag or Al orthe like are formed on the surface of the substrate, degradation of themetallized patterns can be prevented. Since the heat resistancetemperature of these metallized patterns are generally no more than 700deg C., the bonding can be performed without degradation of themetallized patterns by bonding at a temperature of no more than 700 degC.

More preferably, the substrate is insulative, first and secondthrough-holes are formed on the substrate, the first conductor region isformed at the first through-hole, and the second conductor region isformed at the second through-hole. In this case, since the first andsecond conductor regions extend from the surface of the substrate onwhich the element mounting surface is formed to the opposite surface,electrical power can be supplied to the first and the second conductorregions from the opposite surface. More preferably, a minimum formationdimension of metal film patterns of the first and/or the secondconductor region is at least 5 microns and less than 100 microns. As aresult, light-emitting elements can be mounted using the flip-chipmethod. More preferably, the dimension is less than 50 microns. Theminimum formation dimension of patterns here refers to the minimumwidths, minimum distances between patterns, and the like in themetallized patterns.

A semiconductor device according to the present invention includes alight-emitting element mounting member as described in any of the above;and a semiconductor light-emitting element mounted on the elementmounting surface. The semiconductor light-emitting element includes amain surface facing the element mounting surface and the substrateincludes a bottom surface positioned opposite from the element mountingsurface. A ratio H/L between a distance H from the bottom surface to theelement mounting surface and a distance L along a direction of a longside of the main surface of the semiconductor light-emitting element isat least 0.3.

In this case, since the ratio H/L between the long-side length L and thedistance H from the bottom surface to the element mounting surface isoptimized, a semiconductor device with high heat dissipation can beobtained. If the ratio H/L between the long-side length L and thedistance H from the bottom surface to the element mounting surface isless than 0.3, the distance H from the bottom surface to the elementmounting surface becomes too small relative to the long-side length L,preventing adequate heat dissipation.

It would be preferable for an electrode to be disposed on the mainsurface side of the semiconductor light-emitting element andelectrically connected to the first and/or the second conductor region.In this case, since the electrode is disposed on the main surface sideand the electrode is directly connected electrically to the first and/orthe second conductor region, the heat generated by the light-emissionlayer, which is the section of the semiconductor light-emitting elementthat especially generates heat, is transmitted directly to the substrateby way of the electrode. As a result, the heat generated by thelight-emission layer is efficiently dissipated to the substrate,providing a light-emitting element mounting member with superior coolingproperties. It would also be preferable for the main surface to have anarea of at least 1 mm².

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows cross-section drawings of a light-emitting elementaccording to a first embodiment of the present invention and across-section drawing of a semiconductor device using the same. FIG. 1Ais a cross-section drawing of a semiconductor device according to oneaspect. FIG. 1B is a cross-section drawing of a semiconductor deviceaccording to another aspect.

FIG. 2 is a perspective drawing of a light-emitting element mountingmember and semiconductor device shown in FIG. 1.

FIG. 3A is a perspective drawing of the semiconductor light-emittingelement shown in FIG. 1. FIG. 3B shows sample outlines shapes of a mainsurface of the element.

FIG. 4 is a flowchart for the purpose of describing a method for makingthe semiconductor device shown in FIG. 1.

FIG. 5 is a cross-section drawing showing a first step of the method formaking the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 6 is a cross-section drawing showing a second step of the methodfor making the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 7 is a plan drawing of a substrate as seen from the directionindicated by the arrow VII in FIG. 6.

FIG. 8 is a cross-section drawing showing a third step of the method formaking the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 9 is a cross-section drawing showing a fourth step of the methodfor making the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 10 is a cross-section drawing showing a fifth step of the methodfor making the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 11 is a cross-section drawing showing a sixth step of the methodfor making the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 12 is a cross-section drawing showing a seventh step of the methodfor making the semiconductor device shown in FIG. 1 through FIG. 3.

FIG. 13 is a cross-section drawing of a light-emitting element mountingmember and semiconductor device using the same according to a secondembodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be described, withreferences to the figures. In the embodiments below, identical orsimilar elements will be assigned like numerals and overlappingdescriptions will be omitted.

First Embodiment

FIG. 1 is a cross-section drawing of a light-emitting element mountingmember according to a first embodiment of the present invention and asemiconductor device using the same. FIG. 1A is a cross-section drawingof a semiconductor device according to one aspect. FIG. 1B is across-section drawing of a semiconductor device according to anotheraspect. FIG. 2 is a perspective drawing of the semiconductor deviceshown in FIG. 1A. FIG. 3 is a perspective drawing of the semiconductorlight-emitting element shown in FIG. 1A. As shown in FIG. 1A, FIG. 2,and FIG. 3, a semiconductor device 100 according to the first embodimentof the present invention includes: a light-emitting element mountingmember 200; and a semiconductor light-emitting element 1 mounted on anelement mounting surface 2 a. The semiconductor light-emitting element 1includes a main surface 1 a facing the element mounting surface 2 a. Inthis example, the main surface 1 a is formed as a rectangle including alonger first side 11 and a shorter second side 12. A substrate 2includes a bottom surface 2 b opposite from the element mounting surface2 a. A distance H from the bottom surface 2 b to the element mountingsurface 2 a and a length L of the first side 11 have a ratio H/L of atleast 0.3.

The light-emitting element mounting member 200 includes the substrate 2and a reflective surface 6 a and is equipped with a reflective member 6and a metal layer 13. The substrate 2 includes: the mounting surface 2 afor mounting a semiconductor light-emitting element 1; and first andsecond conductor regions 21, 22 disposed on the element mounting surface2 a and connected to the semiconductor light-emitting element 1. Thereflective surface 6 a defines an inner space 6 b which houses thesemiconductor light-emitting element 1. The reflective member 6 isdisposed on the element mounting surface 2 a and contains metal. Themetal layer 13 is disposed on the reflective surface 6 a. The reflectivesurface 6 a is sloped relative to the element mounting surface 2 a sothat the diameter of the inner space 6 b is larger away from the elementmounting surface 2 a.

The light-emitting element 200 is further equipped with a bonding layer9 that joins the element mounting surface 2 a and the reflective member6. The bonding layer 9 has a temperature rating of at least 300 deg C.,and the bonding layer 9 melts at a temperature of no more than 700 degC. to bond the element mounting surface 2 a and the reflective member 6.

The substrate 2 is insulative and is formed with first and secondthrough-holes 2 h, 2 i. The first conductor region 21 is disposed on thefirst through-hole 2 h, and the second conductor region 22 is disposedon the second through-hole 2 i. Also, as described above, in thesemiconductor device, the minimum pattern width and the minimum distancebetween patterns for the metal film formed on the element mountingsurface at the first and/or second conductor regions 21, 22 are keptwithin the range of at least 5 microns and less than 10 microns. Thisallows flip-chip light-emitting elements and the like to be mounted. Arange of at least 10 microns and less than 50 microns is preferable. Inparticular, smaller distances are preferable between patterns in thefirst and second conductor regions 21, 22 as long as bad connections areavoided. The reason for this is that reflection efficiency improves whena larger area is metallized. At less than 5 microns, bad connectionstend to form.

Electrode layers 1 b and if are disposed on the main surface 1 a of thesemiconductor light-emitting element 1 and are connected to the firstand second conductor regions 21, 22. The area of the main surface 1 a isat least 1 mm².

The substrate 2 is electrically insulative and formed from a materialwith good heat conductivity. The material can be selected based on theusage environment. For example, the material can be ceramics having asthe main component aluminum nitride (AlN), silicon nitride (Si₃N₄),aluminum oxide (Al₂O₃), boron nitride (BN), silicon carbide (SiC), orthe like. Alternatively, a material that has as the main componentelectrically insulative silicon (Si), or a composite material or acombination of the above can be used.

The substrate 2 acts as a heat sink that dissipates heat. Thus, higherheat conduction is preferable, and a heat conduction rate of at least140 W/m·K would be preferable, with a rate of at least 170 W/m·K beingmore preferable. If a periodic table group III-V compound semiconductorlight-emitting element or a group II-VI compound semiconductorlight-emitting element is to be used for the semiconductorlight-emitting element 1, it would be preferable for the thermalexpansion coefficient (linear expansivity) to be at least 3.0×10⁻⁶/K andno more than 10×10⁻⁶/K in order to match the thermal expansioncoefficient of the light-emitting element.

Au films 3 a, 3 b, 3 are formed on the element mounting surface 2 a. TheAu film 3 serves to improve the bond between the bonding layer 9 and thesubstrate 2. For this reason, the Au film 3 is formed from a materialthat improves the bond between the bonding layer 9 and the substrate 2.The Au film 3 is used since, in this embodiment, nitride aluminum, aceramic, is used for the substrate 2, and Au—Ge is used for the bondinglayer 9. If the material used in the bonding layer is changed, then itwould be possible to form the Au films 3, 3 a, 3 b as layers havingaluminum as the main component or silver as the main component. The Aufilms 3, 3 a, 3 b are formed by plating, vapor deposition, or the like.It would also be possible to interpose an intermediate layer to improvethe bond, e.g., a titanium layer or a platinum layer, between the Aufilms 3, 3 a, 3 b and the element mounting surface 2 a.

Examples of intermediate layers disposed between the element mountingsurface 2 a and the Au films 3, 3 a, 3 b include Ni, Ni—Cr, Ni—P, Ni—B,and NiCo. These can be formed by plating, vapor deposition, or the like.If vapor deposition is to be performed, materials such as Ti, V, Cr, Ni,NiCr alloy, Zr, Nb, Ta can be used. It would also be possible to stackplated layers and/or vapor deposition layers. It would be preferable forthe thickness of the intermediate layer to be at least 0.01 mm and nomore than 5 mm, and more preferably at least 0.1 mm and no more than 1mm.

In this example, it would also be possible to form an intermediatelayer, e.g., formed from a Ti/Pt layered film, between the substrate 2and the Au films 3, 3 a, 3 b. The film containing Ti in this stackedfilm serves as a bonding layer to improve bonding with the substrate 2and is formed so that it comes into contact with the upper surface ofthe substrate 2. The material for the bonding layer does not need to betitanium and can be, for example, vanadium (V), chrome (Cr),nickel-chrome alloy (NiCr), zirconium (Zr), niobium (Nb), tantalum (Ta),or a compound of thereof.

Also, the platinum (Pt) film in the Ti/Pt stacked film is a diffusionbarrier layer and is formed on the upper surface of the Ti film. Thematerial does not need to be platinum (Pt), and can be palladium (Pd),nickel-chrome alloy (NiCr), nickel (Ni), molybdenum (Mo), copper (Cu),or the like.

The Ti/Pt stacked film and the Au films described above are collectivelyreferred to as a metallized film. The metallized film can be formedusing conventional film-forming methods described above. For example,vapor deposition, sputtering, or plating can be used. The patterning ofthe Ti/Pt stacked film and the Au films can be performed using metalmasking, dry etching, chemical etching, or lift-off involvingphotolithography. These methods are suitable when forming fine patternsrestricted to less than 100 microns or less than 50 microns.

It would be preferable for the thickness of the titanium (Ti) film inthe Ti/Pt stacked film to be at least 0.01 mm and no more than 1.0 mm,and the thickness of the platinum (Pt) film to be at least 0.01 mm andno more than 1.5 mm.

The thickness of the substrate 2, i.e., the distance H from the bottomsurface 2 b to the element mounting surface 2 a, can be set up accordingto the dimensions of the semiconductor element 1, but, as an example,the distance H can be set to at least 0.3 mm and no more than 10 mm.

The semiconductor light-emitting element 1 is disposed so that it comesinto contact with the Au films 3 a, 3 b. The semiconductorlight-emitting element 1 can be formed from a group II-VI compoundsemiconductor light-emitting element or a group III-V compoundsemiconductor light-emitting element. The group II elements here includezinc (Zn) and cadmium (Cd). The group III elements include boron (B),aluminum (Al), gallium (Ga), and indium (In). The group V elementsinclude nitrogen (N), phosphorous (P), arsenic (As), and antimony (Sb).The group VI elements include oxygen (O), sulfur (S), selenium (Se), andtellurium (Te). The semiconductor light-emitting element 1 can be formedas a compound semiconductor that is GaAs-based, InP-based, GaN-based, orthe like.

Through-holes 2 h, 2 i are formed as via holes on the substrate 2. Theconductors used to fill the through-holes 2 h, 2 i form the first andsecond conductor regions 21, 22. The main component for the conductor(via fill) is preferably a metal with a high melting point, particularlytungsten (W) or molybdenum (Mo). It would also be possible to furtherinclude a transitional metal such as titanium (Ti) or a glass componentor substrate material (e.g., aluminum nitride (AlN)). Also, thethrough-holes 2 h, 2 i do not need to be filled with conductor if theinner surfaces thereof are metallized by plating or the like.

The surface roughness of the element mounting surface 2 a is preferablyno more than 1 micron Ra and more preferably no more than 0.1 micron Ra.The flatness is preferably no more than 5 microns and more preferably 1micron. If the Ra exceeds 1 micron or the flatness exceeds 5 microns,gaps tend to form between the semiconductor light-emitting element 1 andthe substrate 2 during bonding, leading to reduced cooling of thesemiconductor light-emitting element. Surface roughness Ra and theflatness are defined according to JIS standards (JIS B0601 and JISB0621, respectively).

The compound semiconductors described above are examples of materialsfor the semiconductor light-emitting element 1 of the present invention,but it would also be possible to stack these layers or bulks on asubstrate such as a sapphire substrate. The light-emitting section canbe at either the top surface or the bottom surface. In this embodiment,the light-emitting layer 1 c is disposed on the substrate side. Sincethe light-emitting layer 1 c, which is the heat-generating section, isdisposed closer to the substrate, heat dissipation for the semiconductorelement can be improved.

A metallized layer, e.g., an electrode layer and insulation layer formedfrom silicon oxide film (SiO₂) can be formed on the surface of thesemiconductor light-emitting element 1 disposed on the substrate 2. Itwould be preferable for the thickness of the gold (Au) serving as theelectrode layer to be at least 0.1 microns and no more than 10 microns.

The semiconductor light-emitting element 1 includes: a base unit 1 eformed from sapphire or the like; a semiconductor layer 1 d in contactwith the base unit 1 e; a light-emitting layer 1 c in contact with asection of the semiconductor layer 1 d; a semiconductor layer 1 g incontact with the light-emitting layer 1 c; an electrode layer 1 b incontact with the semiconductor layer 1 g; and an electrode layer 1 f incontact with the semiconductor layer 1 d.

The structure of the semiconductor light-emitting element 1 is notrestricted to what is shown in FIG. 1A. For example, it would also bepossible to have a structure as shown in FIG. 1B in which the electrodelayer 1 f, the semiconductor layer 1 d, the light-emitting layer 1 c,the semiconductor layer 1 g, and the electrode layer 1 b are stacked. Inthis case, electrodes are present on both the front and back of thesemiconductor light-emitting element 1, and the electrode layer 1 b isconnected by an Au bonding line 71 to the Au film 3 b. In FIG. 1B, onlythe first conductor region is directly bonded to the semiconductorlight-emitting element 1.

As shown in FIG. 3A, of the sides that form the main surface 1 a, thefirst side 11 is the long side and the second side 12 is the short side.However, it would also be possible to have the first side 11 be theshort side and the second side 12 be the long side. In this example, themain surface of the semiconductor light-emitting element is rectangular,so the long side corresponds to the length L along the direction of thelong side. The first side 11 extends roughly perpendicular to thedirection in which the light-emitting layer 1 c extends. The second side12 extends roughly parallel to the light-emitting layer 1 c. Also, thefirst side 11 and the second side 12 can be roughly the same length. Ifthe first side 11 and the second side 12 are roughly the same length,the first side 11 is treated as the long side. Furthermore, if the mainsurface 1 a is not rectangular, e.g., if the corners are rounded, thelong side is defined based on an approximation of the main surface 1 ato a rectangle. Also, while this applies to other embodiments of thepresent invention, if the main surface 1 a is rectangular as in thisexample, the opposite surface will generally be roughly the same shape,but this does not need to be the case. Also, as shown in the examples ofmain surface shapes in FIG. 3B, the main surface can be non-rectangular.The length along the direction of the long side of the main surface ofthe semiconductor element of the present invention is measured from theoutline of the image projected in a direction perpendicular to the mainsurface. FIG. 3B 1 through FIG. 3B 5 are examples of this, and theindicated lengths L are the lengths along the direction of the longside. For example, if the shape is a circle or a square, the lengthwould be the diameter or one of the sides, respectively. If the shape isan ellipse, the length of the major axis is used.

In this example, the long-side length L of the semiconductorlight-emitting element 1 corresponds to the length of the first side 11.It would be preferable for the ratio H/L between this length and thedistance H from the bottom surface 2 b to the element mounting surface 2a to be at least 0.3. It would be more preferable for the ratio H/L tobe at least 4.5 and no more than 1.5. It would be even more preferablefor the ratio H/L to be at least 0.5 and no more than 1.25.

The reflective member 6 is disposed so that it surrounds thesemiconductor light-emitting element 1. A material having a thermalcoefficient close to the aluminum nitride forming the substrate 2 isused. For example, the reflective member can have a thermal expansioncoefficient of at least 3×10⁻⁶/K and no more than 7×10⁻⁶/K. It would bepreferable for the reflective member 6 to have a thermal expansioncoefficient of at least 4×10⁻⁶/K and no more than 6×10⁻⁶/K. Furthermore,it would be preferable in terms of ease of processing to use a metal oralloy or a metal composite material. More specifically, the reflectivemember 6 is formed from a Ni—Co—Fe alloy, with the main components beingNi with a proportion of 29% by mass, Co with a proportion of 18% bymass, and Fe with a proportion of 53% by mass.

The reflective surface 6 a is a tapered, sloped surface disposed on thereflective member 6. The reflective surface 6 a forms an angle relativeto the element mounting surface 2 a preferably in the range of 30 deg to70 deg and more preferably in the range of 40 deg to 60 deg. A platinglayer 7 formed from Ni/Au is disposed on the reflective member 6. Thisplating layer is used when an Au-based solder (Au—Ge) is to be used forthe bonding layer 9 and serves to increase the bonding strength betweenthe bonding layer 9 and the reflective member 6. A plating layer 7 canalso be disposed along the entire perimeter of the reflective member 6.

A metal layer 13 is formed to cover the surface of the reflective member6. The metal layer 13 is formed by plating or vapor deposition andserves to let out light emitted from the semiconductor light-emittingelement 1.

The reflective surface 6 a defines the inner space 6 b, and the innerspace 6 b forms a cone shape. The circular cone shape shown in FIG. 2 isan example. However, it would also be possible for the inner space 6 bto be formed as an angular cone shape such as a four-side cone or atriangular cone. Also, the reflective surface 6 a can be formed as acurved surface such as a parabolic surface.

Next, a method for making a semiconductor device 100 shown in FIG. 1through FIG. 3 will be described. FIG. 4 is a flow chart illustratingthe method for making the semiconductor device shown in FIG. 1. FIG. 5through FIG. 12 are figures for the purpose of describing the method formaking the semiconductor device shown in FIG. 3.

Referring to FIG. 4 through FIG. 5, a substrate is produced first (step201). Since the length and width of this type of substrate 2 is verysmall, on the order of a few millimeters, a substrate base with lengthand width of approximately 50 mm is produced and the through holes 2 h,2 i are formed on the substrate base material. The first and secondconductive regions 21, 22 are formed on the through-holes 2 h, 2 i.Then, the substrate base is finely cut to a predetermined size. The sizeof the substrate base in this method can be, for example, 50 mm inwidth, 50 mm in length, and 0.3 mm in thickness. The sintered aluminumnitride, which is the substrate material, is made using a standardmethod. The cutting and splitting the substrate base to a predeterminedsize can, for example, be performed after bonding (step 206) or atanother step.

Next, the surface of the substrate from the second step is abraded (step202). The surface roughness of the abraded substrate surface ispreferably an Ra of no more than 1.0 microns and more preferably no morethan 0.1 microns. The abrading can be performed using a standard methodsuch as with a grinder, sand blasting, sand paper, or other methodsusing abrasive particles.

As shown in FIG. 4, FIG. 6, and FIG. 7, an Au film is formed usingplating or vapor deposition on the element mounting surface 2 a and thebottom surface 2 b of the substrate 2 (step 203). More specifically, inthe case of this embodiment, for example, Ti/Pt is first vaporized toserve as a backing layer and an Au film is vaporized on this. The vapordeposition method can, for example, involve photolithography, whereresist film is formed on the sections of the substrate outside of theregions at which the films are to be formed, with the layers beingformed on the resist film and the substrate. First, the Ti film servingas the bonding layer is vaporized, followed by the Pt film serving asthe diffusion barrier layer, and then finally the Au film, which is theelectrode layer, is vaporized as the outermost layer. Then, lift-off ofthe resist is performed. More specifically, the resist film formed inthe above step is removed along with the films from the bonding layer,the diffusion barrier layer and the electrode layer using a resistremoval fluid. As a result, as shown in FIG. 6 and FIG. 7, the Au films3, 3 a, 3 b, 3 c, 3 d are formed in predetermined patterns on thesubstrate. The Au films 3 a, 3 b are formed at the central section ofthe substrate, and the Au film 3 is formed to surround these films. Byforming the metal films using a method such as photolithography asdescribed above, patterns with pattern dimensions of no more than 100microns can be formed, and it would also be possible to form patternswith dimensions of no more than 50 microns. The dimensions refer to thesmallest distance between patterns, the pattern widths, and the like. Asa result, it is possible to mount peripheral members that requirehigh-precision dimensions such as flip-chip semiconductor light-emittingelements.

The reflective member 6 is prepared, as shown in FIG. 4 and FIG. 8. Asdescribed above, the reflective member 6 is formed from a material witha thermal expansion coefficient close to that of aluminum nitride, e.g.,an alloy with low thermal expansion formed from Ni—Co—Fe.

As shown in FIG. 4 and FIG. 9, the reflective surface 6 a is formed byprocessing the reflective member 6 (step 204). The reflective surface 6a expands outward, forming an angle (e.g., 45 deg) relative to thewidest surface of the reflective member 6.

As shown in FIG. 4 and FIG. 10, a plating layer 7 is formed on thereflective member 6 (step 205). The plating layer 7 is an Ni/Au stack.Forming the plating layer 7 along the entire perimeter of the reflectivemember 6 is acceptable.

As shown in FIG. 4 and FIG. 11, the reflective member 6 and thesubstrate 2 are connected (step 206). The bonding layer 9 can be solder,sealing/coating glass, heat-resistant adhesive, or the like, andconnects the reflective member and the substrate at a temperature thatdoes not exceed the temperature tolerance of the metallized patterns. Anexample of solder is Au—Ge solder. The use of solder is preferable dueto bonding strength and its Pb-free content. Examples of heat-resistantadhesives include inorganic adhesives and resin adhesives. An example ofsolder is Ag-based solder. Examples of inorganic adhesives include glassand ceramic adhesives. Examples of resin adhesives include polyimideresins, polyamide-imide resin, epoxy resin, acrylic epoxy resin, andliquid-crystal polymer resin.

As shown in FIG. 4 and FIG. 12, the metal layer 13 is formed, e.g.,through plating or vapor deposition (step 207). The metal layer 13serves to let out light emitted from the semiconductor light-emittingelement, and it would be preferable for the outermost layer to be formedfrom a material with a high reflectivity, e.g., Ag, Al, or metals withthese elements as main components. If the reflectivity of the reflectivemember 6 itself is high, the metal layer 13 can be eliminated. Also, insome cases, the metal layer 13 on the Au film 3 a, 3 b where the elementis mounted may be eliminated in order to improve the reliability of thebond with the semiconductor element.

As shown in FIG. 4 and FIG. 1, the semiconductor light-emitting elementis mounted (step 208). The mounting is performed in this case using aflip-chip connection, with the light-emitting layer 1 c disposed towardthe substrate 2. As a result, the heat generated by the light-emittinglayer 1 c is transferred immediately to the substrate 2, providing goodheat dissipation. Examples of members used in the connection includeSn-based solder such as Sn, Au—Sn, Ag—Sn, and Pb—Sn solder, as well asbumps formed from Au or any of these solders.

In the light-emitting element mounting member 200 and the semiconductordevice 100 using the same according to the present invention asdescribed above, the reflective member 6 contains metal. As a result,the metal layer 13 can be formed directly on the surface of thereflective member 6. Also, if the reflective member 6 is to be processedin the step shown in FIG. 9, the processing is made easy and productioncosts can be reduced.

Second Embodiment

FIG. 13 is a cross-section drawing of a light-emitting element mountingmember and a semiconductor device that uses the same according to asecond embodiment of the present invention. As shown in FIG. 13, in thelight-emitting element mounting member 200 according to the secondembodiment of the present invention, metal films 4, 4 a, 4 b are formedon the element mounting surface 2 a, and the metal films 4, 4 a, 4 b areformed from Ag or Al. In this case, as shown in FIG. 13, it is possibleto have the metal layer 13 formed only on the reflective member 6.

In this case, the same advantages are provided as those of thelight-emitting element mounting member 200 and the semiconductor device100 according to the first embodiment.

WORKING EXAMPLE

A detailed study into the characteristics of the bonding layer 9 bondingthe substrate 2 and the reflective member 6 was performed using aworking example. Referring to FIG. 1, the reflective member 6 wasattached to the element mounting surface 2 a of the substrate 2 formedfrom aluminum nitride, interposed by the bonding layer 9. The reflectivemember 6 is an Ni—Co—Fe alloy with an Ni proportion of 29% by mass, a Coproportion of 18% by mass, and an Fe proportion of 53% by mass. Also,the dimensions of the reflective member 6 were set to 5 mm×5 mm×1 mm(height×width×thickness).

For the bonding layer 9, the sample 1 through the sample 8 from Table 1were used. TABLE 1 Electrode metallized pattern Sample Material for theBonding Heat Heat degradation No. bonding layer 9 temperature resistance1 resistance 2 Strength (Au film 3) Notes 1 Solder Au—Ge 12% 360° C. ◯ ◯◯ ◯ ⊚ 2 Ag—Cu 28% 780° C. ◯ ◯ ◯ X Discoloration in Au immediately afterbonding; Film thickness reduced 3 Au—Sn 20% 280° C. X X ◯ ◯ Re-meltingof bonding layer when mounting 4 Glass PbO—B₂O₃ 450° C. ◯ ◯ ◯ ◯ 5 Pbfree 650° C. ◯ ◯ ◯ ◯ 6 Adhesive Epoxy resin 130° C. ◯ X ◯ ◯ 7 Inorganic140° C. ◯ ◯ X ◯ Adhesive layer destroyed due to impact 8 Epoxy +inorganic 150° C. ◯ X ◯ ◯

In Table 1, the component content percentages in the “Material for thebonding layer 9” column refer to percent by mass. These bonding layers 9were melted at the “Bonding temperature” in Table 1 to bond thesubstrate 2 and the reflective member 6.

Strength, heat resistance, and deterioration of the electrode metallizedpatterns, were studied for the samples obtained in this manner. Forstrength, the strength (initial strength) when cooled to roomtemperature (25 deg C.) after bonding was measured. Measurements weremade by applying a load to the reflective member 6 from the directionindicated by arrow 51 in FIG. 1 and determining the pressure when thereflective member 6 detaches from the substrate 2. Based on the results,an initial strength of, at least 10 MPa was determined to be good and acircle was entered in the “Strength” column. An “X” was entered forsamples with initial strengths of less than 10 MPa.

To evaluate heat resistance, the bonding layer was left in an atmospherewith a temperature of 300 deg C. for one minute and for 24 hours at thesame temperature. The samples in which the bonding layer 9 did not meltagain or soften and for which the drop in bonding strength, as measuredaccording to the method indicated in FIG. 1, was less than 10% wasevaluated as good and a circle was entered in the “Heat resistance”column. The results from 300 deg C. for one minute was entered in the“Heat resistance 1” column and the result from the same temperature at24 hours was entered in the “Heat resistance 2” column. For samples withbonding strength drops of 10% or more, an “X” was entered in the “Heatresistance” column. The drop in bonding strength was calculated usingthe formula ((A1−A2)/A1), where A1 is the initial strength and A2 is thestrength at room temperature after being heated at 300 deg C.

In this specification, “a bonding temperature of at least 300 deg C.”refers to when the bonding layer 9 does not re-melt or soften even afterthe bonding layer is kept in a 300 deg C. atmosphere for 1 minute andthat has a bonding strength drop of less than 10% when measuredaccording to the method indicated in FIG. 1. The drop in bondingstrength is calculated using the formula ((A1−A2)/A1), where A1 is theinitial strength (bonding strength before the layer is kept in atemperature of 300 deg C.) and A2 is the strength at room temperatureafter being kept in a 300 deg C. atmosphere for 1 minute.

The deterioration of the electrode metallization patterns (Au films 3, 3a, 3 b) was measured as well. More specifically, visual inspections andthickness measurements were performed on the electrode metallizedpatterns after the light-emitting element mounting member 200 was keptin a 300 deg C. atmosphere for 24 hours. Samples in which deteriorationsuch as discoloration did not take place for Au films 3, 3 a, 3 b wereindicated as circles. If there was discoloration in the Au films 3, 3 a,3 b or if the thickness of the Au films 3, 3 a, 3 b decreased, an “X”was indicated.

As shown in Table 1, good results were obtained in the samples 1, 4, 5,6, 7, 8. The samples 1, 4, 5 provided especially good results.

All aspects of the described embodiments present examples and are notmeant to be restrictive. The scope of the present invention is indicatednot in the description above but by the claims of the invention and allmodifications within the scope of the claims and within the scope ofequivalence to these claims are covered by the present invention.

INDUSTRIAL APPLICABILITY

With the present invention, a light-emitting element mounting member anda semiconductor device that uses the same that can be easily processedand that has superior heat dissipation properties can be provided.

1. A light-emitting element mounting member comprising: a substrateincluding an element mounting surface mounting a semiconductorlight-emitting element and first and second conductive regions disposedon said element mounting surface and connected to said semiconductorlight-emitting element; a reflective member made of metal or alloy ormetal composite material including a reflective surface defining aninternal space for housing said semiconductor light-emitting elementdisposed on said element mounting surface; and a metal layer disposed onsaid reflective surface; wherein said reflective surface is slopedrelative to said element mounting surface so that a diameter of saidinternal space is greater away from said element mounting surface.
 2. Alight-emitting element mounting member according to claim 1 furthercomprising a bonding layer bonding said element mounting surface andsaid reflective member wherein: a heat resistance temperature of saidbonding layer is at least 300 deg C.; and said bonding layer melts at atemperature of no more than 700 deg C. and bonds said element mountingsurface and said reflective member.
 3. A light-emitting element mountingsurface according to claim 1 wherein: said substrate is insulative;first and second through-holes are formed on said substrate; said firstconductor region is formed at said first through-hole; and said secondconductor region is formed at said second through-hole.
 4. Asemiconductor device according to claim 1 wherein a minimum formationdimension of metal film patterns of said first and/or said secondconductor region is at least 5 microns and less than 100 microns.
 5. Asemiconductor device comprising: a light-emitting element mountingmember according to claim 1; and a semiconductor light-emitting elementmounted on said element mounting surface; wherein: said semiconductorlight-emitting element includes a main surface facing said elementmounting surface and said substrate includes a bottom surface positionedopposite from said element mounting surface; and a ratio H/L between adistance H from said bottom surface to said element mounting surface anda distance L along a direction of a long side of said main surface ofsaid semiconductor light-emitting element is at least 0.3.
 6. Asemiconductor device according to claim 5 wherein an electrode isdisposed on said main surface side of said semiconductor light-emittingelement and is electrically connected to said first and/or said secondconductor region.
 7. A semiconductor device according to claim 5 whereinsaid main surface has an area of at least 1 mm².